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But ash is the leftovers from that which burns, so what other stuff doesn't burn? Is it possible to burn away all the ash?

Is ash present when burning other things than organical stuff?

I know that plastics just seems to turn liquid and to smoke.

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"In the large majority of the real world uses of combustion, the oxygen (O2) oxidant is obtained from the ambient air and the resultant flue gas from the combustion will contain nitrogen:

CH4 + 2O2 + 7.52N2 → CO2 + 2H2O + 7.52N2 + heat

As can be seen, when air is the source of the oxygen, nitrogen is by far the largest part of the resultant flue gas.

In reality, combustion processes are never perfect or complete. In flue gases from combustion of carbon (as in coal combustion) or carbon compounds (as in combustion of hydrocarbons, wood etc.) both unburned carbon (as soot) and carbon compounds (CO and others) will be present. Also, when air is the oxidant, some nitrogen will be oxidized to various nitrogen oxides (NOx)."http://en.wikipedia.org/wiki/Combustion

"In the large majority of the real world uses of combustion, the oxygen (O2) oxidant is obtained from the ambient air and the resultant flue gas from the combustion will contain nitrogen:

CH4 + 2O2 + 7.52N2 → CO2 + 2H2O + 7.52N2 + heat

As can be seen, when air is the source of the oxygen, nitrogen is by far the largest part of the resultant flue gas.

In reality, combustion processes are never perfect or complete. In flue gases from combustion of carbon (as in coal combustion) or carbon compounds (as in combustion of hydrocarbons, wood etc.) both unburned carbon (as soot) and carbon compounds (CO and others) will be present. Also, when air is the oxidant, some nitrogen will be oxidized to various nitrogen oxides (NOx)."http://en.wikipedia.org/wiki/Combustion

NO.
or·gan·ic
–adjective
1. noting or pertaining to a class of chemical compounds that formerly comprised only those existing in or derived from plants or animals, but that now includes all other compounds of carbon.
2. characteristic of, pertaining to, or derived from living organisms: organic remains found in rocks.
3. of or pertaining to an organ or the organs of an animal, plant, or fungus.
4. of, pertaining to, or affecting living tissue: organic pathology. http://dictionary.reference.com/browse/organic

car·bon
–noun
1. Chemistry. a widely distributed element that forms organic compounds in combination with hydrogen, oxygen, etc., and that occurs in a pure state as diamond and graphite, and in an impure state as charcoal. Symbol: C; atomic weight: 12.011; atomic number: 6; specific gravity: (of diamond) 3.51 at 20°C; (of graphite) 2.26 at 20°C. http://dictionary.reference.com/browse/carbon

NO.
or·gan·ic
–adjective
1. noting or pertaining to a class of chemical compounds that formerly comprised only those existing in or derived from plants or animals, but that now includes all other compounds of carbon.
2. characteristic of, pertaining to, or derived from living organisms: organic remains found in rocks.
3. of or pertaining to an organ or the organs of an animal, plant, or fungus.
4. of, pertaining to, or affecting living tissue: organic pathology. http://dictionary.reference.com/browse/organic

car·bon
–noun
1. Chemistry. a widely distributed element that forms organic compounds in combination with hydrogen, oxygen, etc., and that occurs in a pure state as diamond and graphite, and in an impure state as charcoal. Symbol: C; atomic weight: 12.011; atomic number: 6; specific gravity: (of diamond) 3.51 at 20°C; (of graphite) 2.26 at 20°C. http://dictionary.reference.com/browse/carbon

b (1): of, relating to, or containing carbon compounds (2): relating to, being, or dealt with by a branch of chemistry concerned with the carbon compounds of living beings and most other carbon compounds

Yep, But I thought it might be of interest to the OP to know what some of the "other stuff" is.

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Yeah, thanks

I just stumbled upon the question when I thought about how fascinating it was that when things burn you can see what it is made of (carbon based) since it doesn't burn as easily , then I just wondered what all the ash was.

So the other things are turned into gas (and smoke), but ash are the things that just simply won't burn.

If you heated it tremendously it would burn though (right?), how tremendously would you need to heat ash for it to burn? - depends on the things in it of course, but generally?

I just stumbled upon the question when I thought about how fascinating it was that when things burn you can see what it is made of (carbon based) since it doesn't burn as easily , then I just wondered what all the ash was.

So the other things are turned into gas (and smoke), but ash are the things that just simply won't burn.

If you heated it tremendously it would burn though (right?), how tremendously would you need to heat ash for it to burn? - depends on the things in it of course, but generally?

Click to expand...

Ash is basically a residue resulted from an incomplete combustion. What are ash
made of is basically depends on:
1. the element that composed the material that you burn (of course).
2. the oxygen available for the combustion
3. the temperature you use for the combustion.

That is said, if the material composed of organic (including organic carbon)
and anorganic (including anorganic carbon), and you burn with insufficient
oxygen, you will likely get the organic carbon, anorganic carbon (carbon in
anorganic compound) and the rest of the anorganic (minerals) in the ash.
If you increase the oxygen until it is more than its stoichiometric requirement,
you can burn all the organic carbon as well. However, if the temperature is
low enough, you will still get the anorganic carbon and other anorganic /
minerals in the ash.

Here is an example of ash composition resulted from combustion of different
woods and different temperature (600 vs 1300 oC):

It depends, of course, on what the original material was. A common one, wood, also leaves a fair amount of phosphorus and potassium compounds in the ash.

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Because ash mostly composed of mineral residue (that is the minerals which
compose the original material but left unburnt), such as phosphorous (P) and
potassium (K), such ashes are often used as fertilizer because it contains
nutrient needed for plant growth (N, P, K, etc). It is also common to use ash
for potash production, provided the ash contain potash (K) mineral.